Came across this and thought it’d be relevant here — Sons are doing a free product testing scheme for UK men. They’re giving away Biotin capsules (for hair growth support), Thickening Clay or a Conditioner, completely free. You apply, and if selected they post the product straight to your door. No purchase needed. UK men only: Sons - Become a Product Tester
They’re offering some free hair products in the UK, including biotin, but remember that biotin’s effects on hair growth are minor unless you have a deficiency. Thickening products can help hair look fuller but won’t treat hair loss causes like AGA.